1. Field of the Invention
The present invention relates to a telephone system which is composed of a set of a master unit and a slave unit and provided with a function of recognizing a caller telephone number, and more particularly relates to a technology for protecting privacy from being infringed. Although the telephone system of the invention is mainly a cordless telephone, a master unit may be provided with a facsimile apparatus, as a master unit.
2. Description of the Related Art
As a telephone system which is ready for a number display service (a caller telephone number display service) and a modem dial-in service, there is provided a telephone system whose master unit and slave unit are both provided with a function of storing a caller telephone number. Further, there is also provided a telephone system which is provided with a function of setting a called terminal between a master unit and a slave unit for each caller telephone number.
These telephone systems are disclosed in Japanese Unexamined Patent Publication JP-A 5-191497 (1993). The telephone systems disclosed in this publication that utilize a selective calling system are equipped with a management table where identification numbers which are respectively associated with a master unit and a slave unit are registered. When a call comes in, the master unit compares the telephone number of the incoming call with the identification numbers stored in the management table. In the case where the telephone number matches one of the identification numbers, only the master unit or slave unit that is associated with the identification number is called, and in the case where the telephone number does not match any of the identification numbers, both the master unit and the slave unit are called.
In the conventional telephone systems which are ready for the number display service, the master unit is absolutely capable of storing a history of incoming caller telephone numbers and displaying it, with the result that a caller telephone number which comes in for the slave unit can be known at the master unit and privacy is sometimes invaded.